Study of charmonium production in b -hadron decays and first evidence for the decay B s 0 → ϕ ϕ ϕ

Using decays to ϕ -meson pairs, the inclusive production of charmonium states in b -hadron decays is studied with pp collision data corresponding to an integrated luminosity of 3.0 fb - 1 , collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. Denoting by B C ≡ B ( b → C X ) × B ( C → ϕ ϕ ) the inclusive branching fraction of a b hadron to a charmonium state C that decays into a pair of ϕ mesons, ratios R C 2 C 1 ≡ B C 1 / B C 2 are determined as R η c ( 1 S ) χ c 0 = 0.147 ± 0.023 ± 0.011 , R η c ( 1 S ) χ c 1 = 0.073 ± 0.016 ± 0.006 , R η c ( 1 S ) χ c 2 = 0.081 ± 0.013 ± 0.005 , R χ c 0 χ c 1 = 0.50 ± 0.11 ± 0.01 , R χ c 0 χ c 2 = 0.56 ± 0.10 ± 0.01 and R η c ( 1 S ) η c ( 2 S ) = 0.040 ± 0.011 ± 0.004 . Here and below the first uncertainties are statistical and the second systematic. Upper limits at 90% confidence level for the inclusive production of X(3872), X(3915) and χ c 2 ( 2 P ) states are obtained as R χ c 1 X ( 3872 ) < 0.34 , R χ c 0 X ( 3915 ) < 0.12 and R χ c 2 χ c 2 ( 2 P ) < 0.16 . Differential cross-sections as a function of transverse momentum are measured for the η c ( 1 S ) and χ c states. The branching fraction of the decay B s 0 → ϕ ϕ ϕ is measured for the first time, B ( B s 0 → ϕ ϕ ϕ ) = ( 2.15 ± 0.54 ± 0.28 ± 0 . 21 B ) × 10 - 6 . Here the third uncertainty is due to the branching fraction of the decay B s 0 → ϕ ϕ , which is used for normalization. No evidence for intermediate resonances is seen. A preferentially transverse ϕ polarization is observed. The measurements allow the determination of the ratio of the branching fractions for the η c ( 1 S ) decays to ϕ ϕ and p p ¯ as B ( η c ( 1 S ) → ϕ ϕ ) / B ( η c ( 1 S ) → p p ¯ ) = 1.79 ± 0.14 ± 0.32 .

Measurement of B_{s}^{0} and D_{s}^{-} Meson Lifetimes

We report on a measurement of the flavor-specific B_{s}^{0} lifetime and of the D_{s}^{-} lifetime using proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to 3.0  fb^{-1} of integrated luminosity. Approximately 407 000 B_{s}^{0}→D_{s}^{(*)-}μ^{+}ν_{μ} decays are partially reconstructed in the K^{+}K^{-}π^{-}μ^{+} final state. The B_{s}^{0} and D_{s}^{-} natural widths are determined using, as a reference, kinematically similar B^{0}→D^{(*)-}μ^{+}ν_{μ} decays reconstructed in the same final state. The resulting differences between widths of B_{s}^{0} and B^{0} mesons and of D_{s}^{-} and D^{-} mesons are Δ_{Γ}(B)=-0.0115±0.0053(stat)±0.0041(syst)  ps^{-1} and Δ_{Γ}(D)=1.0131±0.0117(stat)±0.0065(syst)  ps^{-1}, respectively. Combined with the known B^{0} and D^{-} lifetimes, these yield the flavor-specific B_{s}^{0} lifetime, τ_{B_{s}^{0}}^{fs}=1.547±0.013(stat)±0.010(syst)±0.004(τ_{B})  ps and the D_{s}^{-} lifetime, τ_{D_{s}^{-}}=0.5064±0.0030(stat)±0.0017(syst)±0.0017(τ_{D})  ps. The last uncertainties originate from the limited knowledge of the B^{0} and D^{-} lifetimes. The results improve upon current determinations.

Observation of the Decays Λ_{b}^{0}→χ_{c1}pK^{-} and Λ_{b}^{0}→χ_{c2}pK^{-}

The first observation of the decays Λ_{b}^{0}→χ_{c1}pK^{-} and Λ_{b}^{0}→χ_{c2}pK^{-} is reported using a data sample corresponding to an integrated luminosity of 3.0  fb^{-1}, collected by the LHCb experiment in pp collisions at center-of-mass energies of 7 and 8 TeV. The following ratios of branching fractions are measured: B(Λ_{b}^{0}→χ_{c1}pK^{-})/B(Λ_{b}^{0}→J/ψpK^{-})=0.242±0.014±0.013±0.009,B(Λ_{b}^{0}→χ_{c2}pK^{-})/B(Λ_{b}^{0}→J/ψpK^{-})=0.248±0.020±0.014±0.009,B(Λ_{b}^{0}→χ_{c2}pK^{-})/B(Λ_{b}^{0}→χ_{c1}pK^{-})=1.02±0.10±0.02±0.05,where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty on the branching fractions of the χ_{c1}→J/ψγ and χ_{c2}→J/ψγ decays. Using both decay modes, the mass of the Λ_{b}^{0} baryon is also measured to be m_{Λ_{b}^{0}}=5619.44±0.28±0.26  MeV/c^{2}, where the first and second uncertainties are statistical and systematic, respectively.

First Observation of a Baryonic B_{s}^{0} Decay

We report the first observation of a baryonic B_{s}^{0} decay, B_{s}^{0}→pΛ[over ¯]K^{-}, using proton-proton collision data recorded by the LHCb experiment at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0  fb^{-1}. The branching fraction is measured to be B(B_{s}^{0}→pΛ[over ¯]K^{-})+B(B_{s}^{0}→p[over ¯]ΛK^{+})=[5.46±0.61±0.57±0.50(B)±0.32(f_{s}/f_{d})]×10^{-6}, where the first uncertainty is statistical and the second systematic, the third uncertainty accounts for the experimental uncertainty on the branching fraction of the B^{0}→pΛ[over ¯]π^{-} decay used for normalization, and the fourth uncertainty relates to the knowledge of the ratio of b-quark hadronization probabilities f_{s}/f_{d}.

Measurement of the CP Violation Parameter A_{Γ} in D^{0}→K^{+}K^{-} and D^{0}→π^{+}π^{-} Decays

Asymmetries in the time-dependent rates of D^{0}→K^{+}K^{-} and D^{0}→π^{+}π^{-} decays are measured in a pp collision data sample collected with the LHCb detector during LHC Run 1, corresponding to an integrated luminosity of 3  fb^{-1}. The asymmetries in effective decay widths between D^{0} and D[over ¯]^{0} decays, sensitive to indirect CP violation, are measured to be A_{Γ}(K^{+}K^{-})=(-0.30±0.32±0.10)×10^{-3} and A_{Γ}(π^{+}π^{-})=(0.46±0.58±0.12)×10^{-3}, where the first uncertainty is statistical and the second systematic. These measurements show no evidence for CP violation and improve on the precision of the previous best measurements by nearly a factor of two.

Search for the Decays B_{s}^{0}→τ^{+}τ^{-} and B^{0}→τ^{+}τ^{-}

A search for the rare decays B_{s}^{0}→τ^{+}τ^{-} and B^{0}→τ^{+}τ^{-} is performed using proton-proton collision data collected with the LHCb detector. The data sample corresponds to an integrated luminosity of 3  fb^{-1} collected in 2011 and 2012. The τ leptons are reconstructed through the decay τ^{-}→π^{-}π^{+}π^{-}ν_{τ}. Assuming no contribution from B^{0}→τ^{+}τ^{-} decays, an upper limit is set on the branching fraction B(B_{s}^{0}→τ^{+}τ^{-})<6.8×10^{-3} at the 95% confidence level. If instead no contribution from B_{s}^{0}→τ^{+}τ^{-} decays is assumed, the limit is B(B^{0}→τ^{+}τ^{-})<2.1×10^{-3} at the 95% confidence level. These results correspond to the first direct limit on B(B_{s}^{0}→τ^{+}τ^{-}) and the world's best limit on B(B^{0}→τ^{+}τ^{-}).

Study of J/ψ Production in Jets

The production of J/ψ mesons in jets is studied in the forward region of proton-proton collisions using data collected with the LHCb detector at a center-of-mass energy of 13 TeV. The fraction of the jet transverse momentum carried by the J/ψ meson, z(J/ψ)≡p_{T}(J/ψ)/p_{T}(jet), is measured using jets with p_{T}(jet)>20  GeV in the pseudorapidity range 2.5<η(jet)<4.0. The observed z(J/ψ) distribution for J/ψ mesons produced in b-hadron decays is consistent with expectations. However, the results for prompt J/ψ production do not agree with predictions based on fixed-order nonrelativistic QCD. This is the first measurement of the p_{T} fraction carried by prompt J/ψ mesons in jets at any experiment.

Measurement of the B_{s}^{0}→μ^{+}μ^{-} Branching Fraction and Effective Lifetime and Search for B^{0}→μ^{+}μ^{-} Decays

A search for the rare decays B_{s}^{0}→μ^{+}μ^{-} and B^{0}→μ^{+}μ^{-} is performed at the LHCb experiment using data collected in pp collisions corresponding to a total integrated luminosity of 4.4  fb^{-1}. An excess of B_{s}^{0}→μ^{+}μ^{-} decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be B(B_{s}^{0}→μ^{+}μ^{-})=(3.0±0.6_{-0.2}^{+0.3})×10^{-9}, where the first uncertainty is statistical and the second systematic. The first measurement of the B_{s}^{0}→μ^{+}μ^{-} effective lifetime, τ(B_{s}^{0}→μ^{+}μ^{-})=2.04±0.44±0.05  ps, is reported. No significant excess of B^{0}→μ^{+}μ^{-} decays is found, and a 95% confidence level upper limit, B(B^{0}→μ^{+}μ^{-})<3.4×10^{-10}, is determined. All results are in agreement with the standard model expectations.

Observation of Five New Narrow Ω_{c}^{0} States Decaying to Ξ_{c}^{+}K^{-}

The Ξ_{c}^{+}K^{-} mass spectrum is studied with a sample of pp collision data corresponding to an integrated luminosity of 3.3  fb^{-1}, collected by the LHCb experiment. The Ξ_{c}^{+} is reconstructed in the decay mode pK^{-}π^{+}. Five new, narrow excited Ω_{c}^{0} states are observed: the Ω_{c}(3000)^{0}, Ω_{c}(3050)^{0}, Ω_{c}(3066)^{0}, Ω_{c}(3090)^{0}, and Ω_{c}(3119)^{0}. Measurements of their masses and widths are reported.

Search for massive long-lived particles decaying semileptonically in the LHCb detector

A search is presented for massive long-lived particles decaying into a muon and two quarks. The dataset consists of proton-proton interactions at centre-of-mass energies of 7 and 8 TeV, corresponding to integrated luminosities of 1 and 2[Formula: see text], respectively. The analysis is performed assuming a set of production mechanisms with simple topologies, including the production of a Higgs-like particle decaying into two long-lived particles. The mass range from 20 to 80 [Formula: see text] and lifetimes from 5 to 100[Formula: see text] are explored. Results are also interpreted in terms of neutralino production in different R-Parity violating supersymmetric models, with masses in the 23-198 GeV/[Formula: see text] range. No excess above the background expectation is observed and upper limits are set on the production cross-section for various points in the parameter space of theoretical models.

Observation of B_{c}^{+}→D^{0}K^{+} Decays

Using proton-proton collision data corresponding to an integrated luminosity of 3.0  fb^{-1}, recorded by the LHCb detector at center-of-mass energies of 7 and 8 TeV, the B_{c}^{+}→D^{0}K^{+} decay is observed with a statistical significance of 5.1 standard deviations. By normalizing to B^{+}→D[over ¯]^{0}π^{+} decays, a measurement of the branching fraction multiplied by the production rates for B_{c}^{+} relative to B^{+} mesons in the LHCb acceptance is obtained, R_{D^{0}K}=(f_{c}/f_{u})×B(B_{c}^{+}→D^{0}K^{+})=(9.3_{-2.5}^{+2.8}±0.6)×10^{-7}, where the first uncertainty is statistical and the second is systematic. This decay is expected to proceed predominantly through weak annihilation and penguin amplitudes, and is the first B_{c}^{+} decay of this nature to be observed.

Measurement of the phase difference between short- and long-distance amplitudes in the [Formula: see text] decay

A measurement of the phase difference between the short- and long-distance contributions to the [Formula: see text] decay is performed by analysing the dimuon mass distribution. The analysis is based on pp collision data corresponding to an integrated luminosity of 3[Formula: see text] collected by the LHCb experiment in 2011 and 2012. The long-distance contribution to the [Formula: see text] decay is modelled as a sum of relativistic Breit-Wigner amplitudes representing different vector meson resonances decaying to muon pairs, each with their own magnitude and phase. The measured phases of the [Formula: see text] and [Formula: see text] resonances are such that the interference with the short-distance component in dimuon mass regions far from their pole masses is small. In addition, constraints are placed on the Wilson coefficients, [Formula: see text] and [Formula: see text], and the branching fraction of the short-distance component is measured.

Observation of the Annihilation Decay Mode B^{0}→K^{+}K^{-}

A search for the B^{0}→K^{+}K^{-} decay is performed using pp-collision data collected by LHCb. The data set corresponds to integrated luminosities of 1.0 and 2.0  fb^{-1} at center-of-mass energies of 7 and 8 TeV, respectively. This decay is observed for the first time, with a significance of more than 5 standard deviations. The analysis also results in an improved measurement of the branching fraction for the B_{s}^{0}→π^{+}π^{-} decay. The measured branching fractions are B(B^{0}→K^{+}K^{-})=(7.80±1.27±0.81±0.21)×10^{-8} and B(B_{s}^{0}→π^{+}π^{-})=(6.91±0.54±0.63±0.19±0.40)×10^{-7}. The first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the B^{0}→K^{+}π^{-} branching fraction used as a normalization. For the B_{s}^{0} mode, the fourth accounts for the uncertainty on the ratio of the probabilities for b quarks to hadronize into B_{s}^{0} and B^{0} mesons.

Observation of the Decay Ξ_{b}^{-}→pK^{-}K^{-}

Decays of the Ξ_{b}^{-} and Ω_{b}^{-} baryons to the charmless final states ph^{-}h^{'-}, where h^{(')} denotes a kaon or pion, are searched for with the LHCb detector. The analysis is based on a sample of proton-proton collision data collected at center-of-mass energies sqrt[s]=7 and 8 TeV, corresponding to an integrated luminosity of 3  fb^{-1}. The decay Ξ_{b}^{-}→pK^{-}K^{-} is observed with a significance of 8.7 standard deviations, and evidence at the level of 3.4 standard deviations is found for the Ξ_{b}^{-}→pK^{-}π^{-} decay. Results are reported, relative to the B^{-}→K^{+}K^{-}K^{-} normalization channel, for the products of branching fractions and b-hadron production fractions. The branching fractions of Ξ_{b}^{-}→pK^{-}π^{-} and Ξ_{b}^{-}→pπ^{-}π^{-} relative to Ξ_{b}^{-}→pK^{-}K^{-} decays are also measured.

Observation of [Formula: see text] and [Formula: see text] decays

The decays [Formula: see text] and [Formula: see text] are observed for the first time using a data sample corresponding to an integrated luminosity of 3.0 fb[Formula: see text], collected by the LHCb experiment in proton-proton collisions at the centre-of-mass energies of 7 and 8[Formula: see text]. The branching fractions relative to that of [Formula: see text] are measured to be [Formula: see text]where the first uncertainties are statistical and the second are systematic.

Measurement of the b-Quark Production Cross Section in 7 and 13 TeV pp Collisions

Measurements of the cross section for producing b quarks in the reaction pp→bb[over ¯]X are reported in 7 and 13 TeV collisions at the LHC as a function of the pseudorapidity η in the range 2<η<5 covered by the acceptance of the LHCb experiment. The measurements are done using semileptonic decays of b-flavored hadrons decaying into a ground-state charmed hadron in association with a muon. The cross sections in the covered η range are 72.0±0.3±6.8 and 154.3±1.5±14.3  μb for 7 and 13 TeV. The ratio is 2.14±0.02±0.13, where the quoted uncertainties are statistical and systematic, respectively. The agreement with theoretical expectation is good at 7 TeV, but differs somewhat at 13 TeV. The measured ratio of cross sections is larger at lower η than the model prediction.

Observation of J/ψϕ Structures Consistent with Exotic States from Amplitude Analysis of B^{+}→J/ψϕK^{+} Decays

The first full amplitude analysis of B^{+}→J/ψϕK^{+} with J/ψ→μ^{+}μ^{-}, ϕ→K^{+}K^{-} decays is performed with a data sample of 3  fb^{-1} of pp collision data collected at sqrt[s]=7 and 8 TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into ϕK^{+}, and four J/ψϕ structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed X(4140) state.

First Experimental Study of Photon Polarization in Radiative B_{s}^{0} Decays

The polarization of photons produced in radiative B_{s}^{0} decays is studied for the first time. The data are recorded by the LHCb experiment in pp collisions corresponding to an integrated luminosity of 3  fb^{-1} at center-of-mass energies of 7 and 8 TeV. A time-dependent analysis of the B_{s}^{0}→ϕγ decay rate is conducted to determine the parameter A^{Δ}, which is related to the ratio of right- over left-handed photon polarization amplitudes in b→sγ transitions. A value of A^{Δ}=-0.98_{-0.52}^{+0.46}_{-0.20}^{+0.23} is measured. This result is consistent with the standard model prediction within 2 standard deviations.

Measurement of CP Violation in B^{0}→D^{+}D^{-} Decays

The CP violation observables S and C in the decay channel B^{0}→D^{+}D^{-} are determined from a sample of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 3  fb^{-1}. The observable S describes CP violation in the interference between mixing and the decay amplitude, and C parametrizes direct CP violation in the decay. The following values are obtained from a flavor-tagged, decay-time-dependent analysis: S=-0.54_{-0.16}^{+0.17}(stat)±0.05(syst), C=0.26_{-0.17}^{+0.18}(stat)±0.02(syst). These values provide evidence for CP violation at a significance level of 4.0 standard deviations. The phase shift due to higher-order standard model corrections is constrained to a small value of Δϕ=-0.16_{-0.21}^{+0.19}  rad.

Search for Higgs-like bosons decaying into long-lived exotic particles

A search is presented for massive long-lived particles, in the 20-60 [Formula: see text] mass range with lifetimes between 5 and 100 [Formula: see text]. The dataset used corresponds to 0.62[Formula: see text] of proton-proton collision data collected by the LHCb detector at [Formula: see text]. The particles are assumed to be pair-produced by the decay of a Higgs-like boson with mass between 80 and 140 [Formula: see text]. No excess above the background expectation is observed and limits are set on the production cross-section as a function of the long-lived particle mass and lifetime and of the Higgs-like boson mass.

Search for Structure in the B_{s}^{0}π^{±} Invariant Mass Spectrum

The B_{s}^{0}π^{±} invariant mass distribution is investigated in order to search for possible exotic meson states. The analysis is based on a data sample recorded with the LHCb detector corresponding to 3  fb^{-1} of pp collision data at sqrt[s]=7 and 8 TeV. No significant excess is found, and upper limits are set on the production rate of the claimed X(5568) state within the LHCb acceptance. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the B_{s}^{0}π^{±} final state. The same limits also apply to a possible exotic meson decaying through the chain B_{s}^{*0}π^{±}, B_{s}^{*0}→B_{s}^{0}γ where the photon is excluded from the reconstructed decays.

Evidence for Exotic Hadron Contributions to Λ_{b}^{0}→J/ψpπ^{-} Decays

A full amplitude analysis of Λ_{b}^{0}→J/ψpπ^{-} decays is performed with a data sample acquired with the LHCb detector from 7 and 8 TeV pp collisions, corresponding to an integrated luminosity of 3  fb^{-1}. A significantly better description of the data is achieved when, in addition to the previously observed nucleon excitations N→pπ^{-}, either the P_{c}(4380)^{+} and P_{c}(4450)^{+}→J/ψp states, previously observed in Λ_{b}^{0}→J/ψpK^{-} decays, or the Z_{c}(4200)^{-}→J/ψπ^{-} state, previously reported in B^{0}→J/ψK^{+}π^{-} decays, or all three, are included in the amplitude models. The data support a model containing all three exotic states, with a significance of more than three standard deviations. Within uncertainties, the data are consistent with the P_{c}(4380)^{+} and P_{c}(4450)^{+} production rates expected from their previous observation taking account of Cabibbo suppression.